Braess’s Paradox in Real Life: Improving Traffic by Removing Roads
From class, Braess’s Paradox occurs when adding a new road to a traffic network actually decreases the effectiveness of the network, or adds more time to the average traveler’s trip. This can be seen with the example from class where the new Nash Equilibrium of a traffic network after adding a new road increased the average travel time from 1.8 to 2 hours. When I first heard this conclusion I was very confused. However, the result is actually intuitive because in order for the socially optimal network to occur each individual driver would need to have knowledge of every other driver, and not be thinking of their individually optimal (and selfish) choice. In the real world each driver would be thinking selfishly and the coordination required for the socially optimal choice is just not realistic. In fact according to the Scientific American article, researchers focusing on traffic in Boston found that selfish drivers actually wasted 30% more time than the socially optimal route.
One potential way to improve the flow of traffic is to use the inverse of Braess’s Paradox. If Braess’s Paradox is true then the inverse is also true, meaning removing roads may actually improve the overall flow of traffic. In this case removing a road decreases the options a driver has when choosing a route, so they are “pushed” towards the socially optimal route. For example in Seoul city planners removed a large six lane highway and replaced it with a park. Contrary to the expectations of many experts, the flow of traffic increased. Before this although the idea of Braess’s paradox was out there, it was never given much serious attention by city planners. Perhaps more research could be done regarding this to improve traffic.
Going off of Braess’s paradox, other “counterintuitive” ideas have been considered as ways to improve traffic. One such idea is eliminating all street markings and traffic lights and using “shared roads.” The idea is this improves both safety and traffic because it makes drivers slow down and pay attention to their surroundings because they are in such a chaotic environment. Therefore, the drivers think less selfishly and more so for the “greater good” and closer to the socially optimal route. Studies done in Northern Europe, where there are such streets, supports this conclusion. However, one counter argument could be the margin of error is much higher with shared streets because one bad driver could cause much more harm if there were no rules. Moving forward as more modern and efficient cities and roads are being designed, ideas such as Braess’s paradox should be seriously considered.
Source:
https://www.scientificamerican.com/article/removing-roads-and-traffic-lights/